1. Arizona Cooperative Fish and Wildlife Research Unit University of Arizona School of Natural Resources and the Environment 1064 East Lowell Street, Room N315 Tucson Arizona 85721 USA
2. U.S. Geological Survey Grand Canyon Monitoring and Research Center 2255 North Gemini Drive Flagstaff Arizona 86001 USA
3. U.S. Geological Survey Arizona Cooperative Fish and Wildlife Research Unit University of Arizona School of Natural Resources and the Environment 1064 East Lowell Street, Room N315 Tucson Arizona 85721 USA